Motor-control system.



G. T. EAGAR. MOTOR CONTROL SYSTEM.

APPLICATION FILED UNE 9, 1910.

1,072,440, V Patented Sept. 9, 1913.

Witnesses: Inventor UNITED sTATEs PATENT OFFICE.

GEORGE T. EAGAR, 0F BALLSTON SPA, NEW" YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

MOTOR-CONTROL SYSTEM.

Specification of Letters Patent.

Patented Sept. 9, 1913.

Application filed June 9, 1910. Serial N 0. 565,979.

To all whom it may concern:

Be it known that I, GEORGE T. EAGAR, a

citizen of the United States, residing at Ballston Spa, county of Saratoga, State of New York, have invented certain new and useful Im rovements in Motor-Control Systems, of which the following is a specification.

My invention relates to systems of control for electric motors and particularly to systems of the type in which after the motor is connected to the source of current the potential applied thereto is increased automatically under the control of overload responsive means which limits the rate at which the potential applied to the motor is increased. In systems of control of this type in which resistance is initially connected in series with the motor and is short-circuited section by section automatically under the control of overload devices, it may happen, if for any reason the load on the motor is so excessive that the motor does not start, that the control apparatus will not shortcircuit the sections of resistance and the lat ter may be unduly heated "with injury'to them or to the surrceqding objects. For example, in the case of an automatic current limit starter for a motor-driven pump, it an attempt is made to start the motor when the pump is stuck by being frozen, the current limit. devices of the starter will preventthe latter from notching up that is cutting out the resistance, and the motor mi ht be left stationary and connected to the source with all the resistance in circuit for an indefinite period of time, since under this condition the current in the motor circuit might not be sutlicient to blow fuses or operate other protective devices interposed in the circuit.

It is an object of my invention to overcome the defects in current-limit control svstems. above referred to, and to this end I provide means for rendering a current-limit controller inoperative if the same is not moved from its initial to its final position within a certain interval of time.

In the particular embodiment of my invention herein illustrated, I have provided an automatic current-limit starter of the contactor type with a time limit relay which is energized when the starting master-switch is closed and which interrupts the actuating circuit to the contactors if the last contactor, which is arranged to de'elnerg'i'ze the relay,

does not close within a certain iiiterval of time after the closing of the starting switch. The time-limit relay, therefore, positively prevents the resistances from being connect- Ved in the motor circuitfor more than a certain interval of time without interruption of the current.

The drawing illustrates diagralnmatitailly a system of control having my invention enibodied therein.

The automatic motor starting system shown in this application is of the general type covered by my co-pending application Serial No. 480,481, filed February 27, 1909, and assigned to the same assiguee as this application. I

The motor to be controlled is shown diagranumitically as of the compound type havmg an armature A, series field I and shunt iicld 1", although itmightequally well be oi any other type. The source of current supply both for the motor and for the control circuits is indicated at 'l. The voltage applied to the motor in starting is increased by cutting out successively three sections of starting resistance R It and R. A line contactor ll is arranged when closed to complete a circuit from the source '1, through the resistance It, It and R, the armature A and series field I! of the motor, the shunt field being at the same time energized. The sections of resistance lt It and R are short-circuited by contactors 1, 2 and 3 which may be of any suitable design. The contactors L, 1 and 2 are provided with auxiliary switch attachments oi the kind shown and described in my co-pending application above referred to. Briefly stated, these auxiliary switch attachments each comprise fixed cont acts 5 bridged by a movable ontact mcmher 6 carried by a rod 7 mechanically connccted to the movable member of the corn tactor, so that when the latter is in its open position the contacts 5 and (5 will be held open, audwhen the nu 'able member of the cont actor is in its closed position said contacts 5 and 6 will be permitted to close, unless the rod 7 is maintained in its raised position by the magnetizing effect of the coil which surrounds the core 9 of magnetic material carried by said rod. In the particular system shown the magnetizing coil 10 of the auxiliary switch cooperating with the contactor L is permanently connected to the source in series with the armature and series field and. when the line contactor L is closed this coil 10 is connected in shunt to all of the starting resistance,'as will be clear from the diagram;

The magnet coils 11 coii'perating with the auxiliary switch attachments of the contactors l and Zare connected in series and are located directly in the motor circuit. The actuating circuit 13 of the contactors is connected to the positive side of the source, and located in this circuit are the contacts 14; which are bridged by the contact disk 15 forming part of the relay O. This relay has an actuating coil 16 and a movable core 17 which is retarded in its upward movement by a dash-pot 18 which, however, permits said core to fall freely. lVhen the core 17 of the relay 0 approaches the limit of its upward movement, it engages with stem 20 projecting downwardly from the contact disk 15, and lifts said disk, thereby interrupting the actuating circuit to the contactors. The actuating coil 16 of the relay 0 is connected across the source through the starting switch K and through contacts 21 on the cnntactor 3 opened by said contactor in closing. The arrangement of control circuits for the actuating coils of the contactors will be apparent from the diagram, it being noted that the actuating coil of contactor L is connected between the actuating wire 13 and the return wire 22, and that the actuatingf coils of contactors 1, 2 and 3 are connected between the actuating wire 13 and the return wire 22, through the contacts controlled by the auxiliary switch attachments of the contacts L, 1 and 2 respectively. As in the case of the control system shown in my co-pending application above referred to, the contactors 1 and 2 in closing shortcircuit not only the sections of resistance controlled by them but also a portion of the magnetizing coils of their auxiliary switch. attachments. The connection of the system to the source is controlled by a masterswitch W.

The mode of operation of the control system which I have shown will be obvious from the foregoing andfrom an inspection of the diagram.

Assuming that. the master-switch W is closed and that the starting switch K is also closed in order to start the motor, the actuating wire 13 is connected to the positive side of the source and current flows through the actuating coil of the contactor L and thence through the return wire 22 to the negative side of the source; the contactor L therefore closes and the motor is connected to the source with all the starting resistancemain switch W is closed, the magnetizing coil of the auxiliary switch attachment of the contactor L is energized and when this contactor has closed the magnetizing effect of this coil will hold. its cotiperating core up and the contacts controlled thereby open if the current in the motor circuit exceeds a certain value. As has been before mentioned, this coil'10, after the contactor L has closed, is connected in shunt to all of the starting resistance and therefore receives current proportional to the current in the motor circuit. If the motor starts and begins to speed up, .the increasing counter electromotive force will cut down the current in the motor circuit, and when this current has been reduced to a certain value the current flowing in the coil 10 will be insutlicient to hold this auxiliary switch open and it will close, thereby completing the circuit for the actuating coil of the contactor 1 and causing closing of the latter. Closing ofthe contactor 1 short-circuits the sections of resistance R and a portion of the coil 11 of the auxiliary switch attachment eotlperating with this contactor. Shortcircuiting of the resistance R will increase the current in the motor circuit and the auxiliary switch attachment of the contactor 1 will not close until the current in the upper half of the coil 11, which is still in the motor circuit,

has decreased to a certain value. When the motor current has decreased to this value, the circuit for the actuating coil of the contactor 2 will be completed and this contactor will close. The mode of operation of the contactors under the control of the currentlimit devices is fully explained in my copending application above referred to and need not be more fully described.

The relay 0 is so designed that the time interval between the energization of its actuating coil 16, by closing of the masterswitch K, and the lifting of the contact disk 15 is great enough to allow plenty of time for the successive closing of the con-" tractors and complete speeding up of the motor if the latter starts and operates in the usual way. If, however, for any reason the motor fails to start and the heavy current in its circuit prevents closing of the auxiliary switch cotiperating with the contactor L and consequently prevents cutting out of the resistance'in the motor circuit, therelay 0 will, after a certain interval of time, interrupt the actuating circuit 13, thereby denergizing the actuating coil of the contactor L and causing the latter to open with resultant interruption of the motor circuit. Under this condition as long as the masterswitch K is left closed the core of the relay 0 will stay up and the actuating circuit will be interrupted. Of course opening of the switch immediately interrupts the circuit through the actuating coil 16 of the relay 0 and the latter drops, thereby allowing its contacts to close and placing the system in condition for another attempt to start the motor. If, on the other hand, the

motor starts in the usual way, the last contactor type, it is of course equally applicable to many other styles of control apparatus, and, in the appended claims, I intend to cover all such applications of my invention and all embodiments which come within the scope -thereof.

What I claim as new and desire to secure by Letters Patent of the United States is 1. The combination with an electric motor, a plurality of contactors arranged to be energized successively to bring the motor to running speed and a time limit relay energized simultaneously with the closing of the motor circuit to effect the opening of said circuit if all "the contactors do not close within a certain interval of time after the,

closing of the motor circuit.

2. The combination with an electric motor, a plurality of contactors arranged to be energized successively to bring the motor to running speed, and a time limit relay energized simultaneously with the first contactor and arranged to effect the opening of said contactor, in case all of the contactors do not close within a certain interval of time after the closing of the first contactor.

3. In combination with a power circuit, a plurality of contactors intended for operation in succession to effect certain connections in said power circuit, overload responsive devices cooperating with said contactors and arranged to retard the successive operation of the latter if the current in the motor circuit, exceeds a certain value, and a time-limit relay energized simultaneously with the first contactor arranged to efi'ect the opening of said contactor if all of said contactors do not close within acertain interval of time after the closing of the first contactor.

4. In combination With a-i'powercircuit, a. plurality of contactors. intended for opera,

tion in succession toiefiect certain 00111180: tions in said power circuit, an actuating circuit for saidcontactors, overload responsive devices cooperating with said contactors and arranged to regulatethe successive closing thereof, a time-limit relay controlling said actuating circuit, and contacts opened by the last contactor for deenergizing said relay, whereby said relay will interrupt said actuating circuit unless all of said contactors close within a certain interval of time after the closing of the first contactor.

5. A control system comprising an electric motor, automatic means for accelerating the motor step by step, means through which energy is normally supplied to actuate the accelerating means and delayed means rendered inoperative by the complete action of the accelerating means for interrupting the supply of energy thereto.

6. A control system comprising an electricmotor, automatic means for accelerating the motor step by step, a switch through which energy is normally supplied to actuate the accelerating means, and delayed means rendered inoperative by the complete action of the accelerating means for openingthe switch.

7. A control system comprising an electric motor, an accelerating resistance and a plurality of. structurally independent accelerating switches therefor, a relay switch throughwhich energy is normally supplied to actuate the accelerating switches and delayed means rendered inoperative by the closure of the accelerating switches for opening the relay switch.

In witness whereof, I have hereunto set my hand this 7th day of June, 1910.

GEORGE T. EAGA-R. Witnesses:

HELEN Onronn, MARGARET E. WOOILLEY. 

